Yep - I obtained one in a trade a couple of months back. It's so tiny that it felt like a toy the first time I got it in hand. It also had a bit thicker an edge geometry than I would have liked so I spent a bit of time re-profiling the edge to suit my intended tasks better: On one side, I did a total convex grind and on the other, I did a fairly flat grind with the shoulder knocked off. The hatchet is used for light chopping and small splitting chores but mostly for a good bit of basic wood shaping/carving. I found that this combination gave a fairly robust edge that would stand up to chopping/splitting while having a more V-ground edge on the side that meets the wood during carving allowed me to have the advantages generally associated with a scandi edge (namely, not as fidgety when push-cutting as the depth of the cut is easy to gauge). You should see the feather-sticks it can make! Practically just as good as my scandi.
Now I only have a 26" GB Scandi and 19" GB SFA to compare it to, so I can't really say much about its handiness compared to a 13-15". When you go below 18" though, you've pretty much decided on a one-handed tool and have thus already decided to compromise chopping power in exchange for ease of carry and finesse. Regardless whether it's 10" or 15", you're not going to be taking on trees/limbs much thicker than 4-5" and will be opting to use your saw to section it out anyways. I'd say the role of a an axe in that length range is more wood-processing (splitting) and finer tasks (basic shaping whilst carving) with a little bit of light chopping. While a 15" would have the advantage of added leverage, I find that my 10"er is perfectly capable of these tasks and is more packable. It's such a small size that I almost always EDC it in my pack and there's a lot to be said about the handiness of a tool that's always with you.
Anyways, for fear of reaching TL;DR territory, I'll cut myself off there and say that if you have any other questions, feel free to ask. I'd also be glad to take some pictures if you need them.
Oh, and to answer your other question: bensbackwoods is my recommended site for buying both wetterlings and GBs. Great prices, great selection, and a lot of other nifty outdoor gear that you might be interested in :thumbup:
